Going from idea to one-off widget is one thing; engineering the widget into a marketable product is quite another. So sometimes it’s instructive to take an in-depth look at a project that was designed from the get-go to be a consumer product, like this power indicating wall outlet cover plate. The fact that it’s a pretty cool project helps too.
Although [Vitaliy] has been working on this project for a while, he only recently tipped us off to it, and we’re glad he did because there’s a lot to learn here. His goal was to build a replacement cover for a standard North American power outlet that indicates how much power is being used by whatever is plugged into it. He set constraints that included having everything fit into the familiar outlet cover form factor, as well as to not require any modification to the existing outlet or rewiring, so that a consumer can just remove the old cover and put on the new one. Given the extremely limited space inside an outlet cover, these were significant challenges, but [Vitaliy] found a way. Current is sensed with two inductors positioned to sense magnetic flux within the outlet, amplified by a differential amp, and power use is calculated by an ATmega328 for display on 10 LEDs. Power for the electronics is tapped right from the outlet wiring terminals by spring clips, and everything fits neatly inside the cover.
It’s a great design, but not without issues. We look forward to seeing [Vitaliy] tackle those problems and bring this to market. For more on what it takes to turn a project into a product, check out our own [Lewin Day]’s story of bringing a guitar effects pedal to market.
So the more you use adds a coefficient greater than 1 so you use more power,
the OCD purists night find this as fodder for objection, its a good start congrats.
Nice idea though I want the option of just one led going up and down at say
x100W or so levels with blink at x10W or some such scaling factor so I can
have fun trying to interpret what the light means whilst I fiddle with the lathe ;-)
Well done though, sure is a market for that with some I know, good luck
I never thought of using a cheap current monitor on a power tool like a lathe or drill but now you’ve got me thinking!
Hey good fun JohnU,
Having been in metal working in my very earliest days dealing with 500T
press brakes, 3m guillotines, 6m lathes and 20m planers it occurs to add
a summing function ie overall KWHr be great for one off client jobbing work
& across a set of tools on the same group of outlets – assuming of course
a managed workforce including some discipline re tool sign on/off…
Then the Joules consumed can be factored into a metric re equipment
depreciation as in wear, repair contribution, insurance etc Such that the
clients final value fee for the job takes that into account so there is no longer
a costing aspect lost in the mass of expenses vs client return on investment :-)
For some smaller shops this might even point to opportunities to reduce costs
and gain competitiveness, for larger machine shops can point to efficiency of
utility and the issue of dead time re holding costs. Lots of other management
issues come to mind, though really only pertinent to size of organisation and
actial throughput vs marketable throughput etc. As I understand it modern
equipment has that potential already, there are many last century tools where
an outlet like this can be useful as a economic measurement tool…
He claims he is measuring power and energy, but I just see power …
Maybe he’s measuring “Dark Energy”, therefore, you won’t “see” it!
B^)
Energy = power X time. E.g kWhr
Thanks for the pertinent reminder Bootstrap :-)
Short of standing there watching and marking time,
I think the comment directly relates an actual Display.
With a minimal number of leds can be done easily
or go a bit extra with 7-segments numeric, there are
of course other permutations :-)
Cheers
What about using something like a 78M6613 ? It does PF correction, and potentially a smaller footprint than the current (ho ho) solution? I’d see BLE or WiFi connectivity as a real bonus for logging — e.g. ESP32. Without logging, I don’t really understand the market for this — why would I want a visual indicator of consumption on a per-socket basis on an on-going basis? And if it’s just for a one-off understanding of an appliance’s consumption, why not use a separate plug-in monitor? Nicely engineered though – I like the bar graph.
Arranging for a shunt resistor inside the outlet cover could be quite difficult.
But yeah, I can’t think of a reason why I’d want a power monitor in outlet cover either..
The changing led modes are confusing. Just add a 7×4 .5CM Display at Top. Show “Load” and then show Watt/Hour Numbers, Show “tod” for Todays Watts Consumed, Show “mon” for Monthly Watts Display for that plug.
Or even just 3 more labeled LEDs that indicate what’s being shown
Unfortunately the space and the amount of power budget available from the simple reactive voltage divider (the only thing that can really fit in there to power electronics) inside prohibits integrating any LCD type of display. Also since all the electronics are under high voltage inside relative to earth, for manufacturing purposes, and UL safety regulations, the less perforated the cover is the better. So small holes for LEDs seemed like offer the best chances in certifying this cover as well less intrusive for the home decor (some people might not want LCD displays every where in their rooms outlet covers). The IoT connectivity is eventually best option here as an upgrade to this design.
After reading his project page, which is an excellent read, his aim was to do this thing while keeping costs low and ease of installation high. His goal was to make a device that was competitive in price to existing units, but easier to use, and I believe he suceeded.
I too think the bargraph idea is hard to interpret for such a wide range (2.5watts to over 2Kwatts) and an LCD would be preferable, but it would increase the cost substantially.
I purchased one of those plug-in units (as mentioned by Vadim below), and I must say I stopped bothering after the first few days of “check this out”. Stuff draws the power it draws, and there is not much you can do about it. Full house monitoring is better, but then how do you tell where the power is going when you do want to shave that few watts?
I like how he has used the center metal (ferrous) bar to measure current. That is very neat. Unfortunately it won’t work for most non-american outlets (I’m from Australia). But it certainly gives me ideas.
Very nice project, and well written up.
I have been using this device for about 5 years.
https://www.amazon.de/Energiekosten-Messgerät-Kontrolle-Stromverbrauchs-Innenbereich/dp/B00LGTW4FI/ref=pd_day0_107_6?_encoding=UTF8&psc=1&refRID=DCJ76F0ED0WRK6ZCVGSM